Hematopoietic stem-cell gene therapy is associated with restored white matter microvascular function in cerebral adrenoleukodystrophy

Blood-brain barrier disruption marks the onset of cerebral adrenoleukodystrophy (CALD), a devastating cerebral demyelinating disease caused by loss of ABCD1 gene function. The underlying mechanism are not well understood, but evidence suggests that microvascular dysfunction is involved. We analyzed cerebral perfusion imaging in boys with CALD treated with autologous hematopoietic stem-cells transduced with the Lenti-D lentiviral vector that contains ABCD1 cDNA as part of a single group, open-label phase 2-3 safety and efficacy study (NCT01896102) and patients treated with allogeneic hematopoietic stem cell transplantation. We found widespread and sustained normalization of white matter permeability and microvascular flow. We demonstrate that ABCD1 functional bone marrow-derived cells can engraft in the cerebral vascular and perivascular space. Inverse correlation between gene dosage and lesion growth suggests that corrected cells contribute long-term to remodeling of brain microvascular function. Further studies are needed to explore the longevity of these effects.


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Replication STARBEAM study related data that supports the findings of this study are available from Bluebird Bio. Restrictions apply to the availability of these data because elements of the data set comprise information proprietary to Bluebird Bio. Any requests for additional data will be considered by all authors and Bluebird Bio. Bluebird requires 30 days from receipt date of the request to consider and respond to data requests. Any requests can be sent to medinfo@bluebirdbio.com. Data not associated with the STARBEAM study and collected at MGH can be shared with interested investigators but are subject to local and national ethics regulations and legal requirements that respect the informed consent forms. The raw imaging data are protected and are not available due to data privacy laws. The data generated in this study are provided in the Source Data file.
Adrenoleukodystrophy (ALD) is a disease linked to the X chromosome. The cerebral phenotype affects male sex. Only patients with male sex were investigated. Gender is not reported in our study.
STARBEAM study: Males aged 17 years and younger (range 4.1 -8.6 years) who have been definitively diagnosed with CALD (by finding elevated levels of VLCFA) who have a MRI Loes score between 0.5 and 9 (inclusive), an NFS ! 1, and gadolinium enhancement on MRI. Patients outside of the STARBEAM trial: Males (age range 0.3-47.3 years) diagnosed with ALD who have a MRI Loes score between 0 and 9 (inclusive at baseline) and available DSC MRI Perfusion imaging as part of routine clinical care.
Participants were recruited by peer to peer physician referral (this study included only boys with no related and no unrelated compatible HSCT donor and therefore have not access to standard of care with allo-HSCT for CALD), referral by Leukodystrophy advocacy groups across the world, self-referral to Dr. Musolino, Dr. Duncan and Dr. Eichler clinics or the sponsor. Open recruitment for the study was published in clinical trials.gov and sponsor websites during the duration of the study. Potential biases are access to internet, ability to speak English by referring team or patient (despite availability of translators to all languages) and inability to travel to the study sites for the screening, treatment and follow up visits. All participants were enrolled after screening multi-PI calls that confirm eligibility on a first come first serve basis. Priority was given to participants with more advance lesions when possible if study drug was available.
The study received ethical approval by the Institutional Review Board of MGH (MGH protocol 2012-P-000132/1). Informed consent was obtained from patients and/or from legal representatives.
By using the means and common standard deviation for ADC, CTH, Kapp, RTH and VA from pilot data and assuming a two-sided alpha-level of 0.05, homogeneous variances for the samples to be compared and a 80.0% power we calculated that small effect sizes can be detected with lesion size and diffusion tensor data (Hedges' g= 0.11) and large effect sizes with perfusion based data (Hedges' g= 1.04-1.25) for the numbers of available patients.
Incomplete magnetic resonance perfusion datasets or those significantly degraded by motion artifacts were excluded from the analysis since algorithmic perfusion analysis would yield nonsensical data. This was pre-established.
Raw perfusion data was analyzed using two algorithms that are both based on vascular models but calculate output based on different imaging parameters. The first uses voxel-wise fitting of a vascular model to individual concentration-time curves obtained from the gradient echo-based DSC MRI data. The second obtained relaxation rate curves from the DSC images of the gradient echo-and another acquired dataset using spin echo-sequences. ROI placement was performed by two independent readers and intra-class correlation coefficient was Reporting for specific materials, systems and methods We require information from authors about some types of materials, experimental systems and methods used in many studies. Here, indicate whether each material, system or method listed is relevant to your study. If you are not sure if a list item applies to your research, read the appropriate section before selecting a response. calculated and evaluated. We also included a group of CALD patients treated with standard of care bone marrow transplant (allo-HSCT) as a positive control. However, ex-vivo our findings are based on the only available human brain sample of a patient treated with allo-HSCT. To date no additional samples (neither allo-HSCT nor gene therapy in CALD patients) are available in the NICHD Brain and Tissue Bank for Developmental Disorders.
The STARBEAM study is a single group study, so no patients were randomized. The standard of care group was recruited from an ongoing observational cohort study. Here, all patients with the required advanced imaging protocols were included. Since we were not able to create a matching cohort, we refrained from directly comparing standard of care treatment with gene therapy. However, we performed comparisons between treated and untreated patient groups. The literature indicates that age is the most important covariate. To control for this, we drew age-matched (by nearest neighbor matching) scans from a larger imaging data base.
For every scan ROI placement were performed blinded to perfusion and clinical data (with the exception of apparent CALD lesions on T2W imaging). CD34+-derived peripheral blood cells from a male patient with confirmed loss of ALDP after treatment with eli-cel.
Loss of ALDP expression was confirmed by flow cytometry and western blot.
Cell lines tested negative for mycoplasma contamination. N/A.

March 2021
Clinical data